Highway maintenance of elevated structures



Nov. 19, 1963 B. LARNER 3,110,981

HIGHWAY MAINTENANCE OF ELEVATED STRUCTURES Filed Sept. 30. 1960 I" THICKURETHANE FOAM *'STEEL SUPPORTING GIRDERS k INVENTOR BERBNARD LARN ERATTORNEY United States Patent Ofitice Nov. 15%, 1963 3,11%,981 IHGHWAYMAENTENANCE F ELEVATE STRUCTUREf-r Bernard Earner, Scotch Plains, NJassignor to Allied Chemical Qorporation, New York, N.Y., a corporationof New York Filed Sept. 34), 196%, Ser. No. 59,611 7 (Ilairns. (Ql.Sit-192) This invention relates to bridges and other elevated structuresand more particularly refers to elevated structures having concretedecks and the treatment of such concrete decks to improve theirroadability and reduce maintenance.

In modern highway type of construction, grade crossings of railroads andother highways are eliminated by use of overpasses and underpasses. Allof this is designed to promote safety and to insure steady flow oftrafiic. Along with this type of construction, however, other problemsare encountered, primarily at the bridges and overand underpasses where,particularly in the United States and Canada, these structures areexposed both top and bottom to early freezing due to sudden changes intemperatures, wind velocities, etc. This creates very hazardousconditions especially when the overland portions of the highways arefree of ice and the tratfic approaches the bridges at normal rates ofspeed which cannot be sustained with safety over the frostandice-covered structures. Highway officials, quick to recognize suchhazards, have, in many instances, found it necessary to post warningsigns at the approaches to these overhead structures warning the trafiic0f the dangerous conditions; such signs often read caution BridgeFreezes Before Highway.

As previously stated, in modern highway construction greater use is madeof overhead structures, such as bridges over streams, and over-passesand underpasses to elimi nate grade crossings of railroads, highways andthe like. There are estimated to be about 100,000 structures of thesetypes in the United States alone. Based on this figure, it is believedthat at least about 75,600 would be subject to frost conditions.

Another serious problem which has arisen as a result of the above typeconstruction has to do with the spalling or cracking and fracturing ofthe concrete bridge decks. In the United States and other countriessubject to frost, this condition has resu ted in early failures of thebridge decks; such failures often occur during the first winter afterinstallation and usually occur within a period of from six months to tWoyears. The repair and maintenance of these structures is very costly andaggravates the safety problems described. Methods of repair include, butare not limited to, patching of the cavities and filling with newconcrete, bituminous concrete and, more recently, with expensive epoxyresin compositions. If the repairs are not made at the early stages ofdeterioration, then complete renewal of the bridge decks with newconcrete or bituminous concrete surfaces is required. It is, of course,impractical to continue adding new surface courses of concrete andbituminous concrete to the bridge decks because of the substantiallyincreased weight which would become a significant danger factor.

In order to minimize the effect of added Weight on these structures, thetendency on the part of highway engineers has been to decrease thethickness where bituminous concrete has been used to resurface thebridge ecks. 'In many such instances, the spalling has continued at theinterface between the bituminous concrete surface and the cementconcrete deck and has caused the former to lose its bond and peel offfrom the deck. The types of maintenance described herein are, of course,

2 very expensive and result in tying up the bridges during extendedperiods. Furthermore, this type of maintenance can only be done duringthe period from approximately May 1 to October 15 in the areas of theUnited States and Canada involved with this problem.

An object of the present invention is to provide a method forretardation of ice formation on the upper surface of a concrete deck ofan elevated structure surfaced with either concrete or a bituminouslayer.

Another object of the present invention is to provide a method for theobtainment of frost conditions on the upper surface of a concrete deckof a bridge surfaced with either concrete or a bituminous layer, similarto the road leading to the bridge.

A further object is to provide a method for materially reducingspall-ing of the concrete deck of an elevated structure.

A still further object is to provide a method of reducing spa'lling andimproving readability of the concrete deck of an elevated structure witha relatively small amount of weight added to the elevated structure.

Another object is to provide an efficient, economical method of reducingspalling and improving readability of a concrete deck of an elevatedstructure. A further object is to provide an improved elevated structurewith a concrete deck having reduced tendency to spalling of the concreteand better roadability. Other objects and advantages will be apparentfrom the following description and accompanying drawing.

l have discovered that spalling of the surface of a concrete deck of anelevated structure and retardation of ice formation on the upper surfacemay be materially reduced, ice formation on the upper surface of thedeck retarded with frost conditions on the upper surface of the decksimilar to the road approaches leading to the deck, by the applicationof a layer of about /2 inch to 3 inches thick, preferably about to 1 /2inches thick, of cellular plastic material, preferably having closedcells and having a density of about 1 to 8 pounds, preferably about 1 /2to 5 pounds, per cubic foot bonded to the underside of the concretesurface of the elevated structure. The eifect of reduced spalling andimproved roadability by the bonding of a layer of cellular plasticmaterial to the underside of the concrete surface is surprising andunexpected because the upper surface of the deck remains exposed to theelements as before and the lower surface, save for the interposition ofthe bonded cellular layer, remains exposed to the elements.

The accompanying drawing diagrammatically illustrates a section of anelevated structure having a concrete deck to which is bonded on itsunderside a layer of cellular plastic material. Referring to thedrawing, the deck, designated by numeral 1, is a reinforced concretedeck about 9 inches thick. The substantially horizontal concrete deck 1exposed to the atmosphere is supported by the usual supporting membersas illustrated by steel support girders 3 and 4. On the underside ofreinforced concrete deck 1 and bonded thereto is a layer 5 of cellularplastic, urethane foam, 1 inch thick and having a density of 4 poundsper cubic foot.

Typical bridge structures for which this development is consideredparticularly applicable are as. follows: the span to be covered may beonly 50 feet where the bridge crosses a small stream, a singleordouble-lane highway or a railroad track. It may, on the other hand, he 1to 1 /2 miles in length where the bridge crosses a large body of water,where the roadway is elevated over marshy or low-lying areas of thecountry or where it passes over built-up areas of cities or villages.The structures may be supported by concrete piers or steel columns. Thebridge decks are usually supported by fabricated longitudinal l-beams,channels or prestressed concrete beams.

a high wind velocities.

Between the longitudinal members are cross-beams usua ly of the sametype but of smaller dimensions. The bridge decks are of poured concretetype with typical reinforcing bars; the thicknesses may vary from 3 to12 inches, depending upon span, weight to be carried and other factors,and are most generally from 6 to 9 inches. Of course, large over-waterspans involve a somewhat different type of supporting structure and areusually of the suspension type; the bridge decks, however, are of thesame type construction as described above.

The heights of the bridges are usually det rminecl by the purpose forwhich they are installed. For overpass of a highway the height isgenerally 12 to 16 feet; for

racer overpass of a railroad about 22 feet minimum; and over water itwould depend on the type of navigation involved and often exceeds 75feet. It can readily be seen that the decks of bridges, being generallyelevated from about 12 to 75 feet or more, are exposed to the weatherboth top and bottom. They are therefore subjected to rapid changes intemperature which may be accentuated by These conditions cause extremeweathering effects on the bridge decks and bring about, for example,rapid freezing and thawing which results in the serious safety problemsand may be a major factor in the spahing of the decks.

The overhead structures to which the present invention applieshaveconcrete decks exposed on their top and bottom sides to theelements. As previously pointed out, in some instances the bridge deckshave been surfaced with a bituminous upper layer in an effort to reducespalling and improve road conditions. The present invention is alsoapplicable to decks which are constructed of concrete with an overlayingbituminous layer and the application of a cellular plastic material tothe underside of such decks improves readability and reduces spalling ofthe concrete.

Examples of cellular plastic suitable for application in the presentinvention are foam from polyurethanes, polystyrenes, polyvinylohloride,phenolics, polyethylene or the like, which materials are well known inthe art. The layer of cellular plastic material may be applied in twomanners. In one instance, preformed slabs of 'cellular plastic materialof about /2 to 3 inches thick (preferably about /4 to 1 /2 inches thick)and having densities of about 1 to 8 pounds (prefer-ably 1 /2 to pounds)per cubic feet, are bonded to the under sides of the bridge decks bymeans of conventional adhesives of the clastorneric or polymeric typedepending upon the specific foam to be used. it is important that thecellular plastic material be bonded to the underside of the concretedeck and securing the slabs by mechanical means such as clamps or thelike are not satisfactory and should not be employed. Preferably,however, the cellular plastic is applied to the underside of theconcrete deck by spraying liquid reactants which upon striking theconcrete underside form a urethane foam which adheres to the concretesurface sprayed without the'use of adhesives. This adhesive bond isgenerally stronger than the foam itself. Production of urethane foam byspraying is well known in the art involving spraying, by means or" thespray gun, an isocyanate and an organic compound having a reactivehydrogen such as a polyester or a polyether which reacts with theisocyanate and in the presence of a blowing agent such as water or analiphatic fluorine hydrocarbon designated in the art as Genetron form acellular foam. The production of urethane foam is known in the art andneedsno extended discussion herein. An important consideration in theuse of the cellular plastic material in accordance with the presentinvention is its light weight. Bridges we designed to bear certain loadsand the addition of a material amount of added weight on thesestructures would obviously be detrimental. Merely for illustrativepurposes, the application of polyurethane having a density of 4 poundsper cubic foot and an inch thick would be equivalent when applied to abridge having if. a surface area of 2,0ilb feet of less than 700 pounds,which amount of weight is insignificant in a structure of that typeparticularly when distributed evenly over the underside. in contrast, alayer of bitumen of the same thickness would impose an added load on thebridge of approximately 50 times greater than the cellular plasticmaterial. An additional advantage in the use of the cellular plasticmaterial concerns aesthetics in that it is adapted to be painted, thesame color as the rest of the bridge, if desired.

in practice, a dual highway-spanning bridge, each half of which is about65 feet wide, 65 feet long and 15 feet high, and having a 9-inch thickconcrete deck resting on prestressed concrete beams and crosspieces, wassprayed on /2 of its underside with approximately 1 inch of polyrethanefoam having a density of about 4 pounds per cubic foot. The formulationfor preparing the foam urethane is as follows:

Parts by weight Plaskon polyester PFR13 Cellufiex" CEF 25 rnulphoren-719 4 Water 4 Nacconate WES-HM Plaskon polyester FIFE-143 is apolyester made from adipic acid, trimethylol propane and the diarninereaction product of an amine with ethylene oxide and is obtainable fromthe Plastics and Coal Chemicals Division of Allied Chemical Corporation.Celluflex CEF (tris(2-chloroethyl)phosphate) is a fire retardantobtainable from Celanese Corporation of America. Emulphor EL-719 is apolyoxyethylated vegetable oil, a non-ionic emulsifier, product ofAntara Division, General Aniline & Film Corporation. Nacconate NEED-HMis a modified toluene diisocyanate obtainable from National AnilineDivision of Allied Chemical Corporation.

The foam was sprayed on the underside of the bridge deck utilizing aninternal mixing spray gun. The spraying equipment was mounted on a3-axle (GMC) truck chassis equipped with a flat body on which wasmounted a conventional gasoline air-compressor (having a capacity inexcess of 100 cubic feet of free air at 100 pounds pressure per minute),a gasoline-operated electric power generator, and a Gar-Wood telescopicplatform from which the spraying was accomplished by the operator.

Another small portion of the bridge, roughly about 50 square feet wascovered by bonding slabs of urethane foam sheets about 1 inch thick. Thebonding material employed was Bondrnaster DL-23A, a neoprene baseadhesive, available from Rubber and Asbestos Corporation.

Examples of organic diisoeyanatc that can be used instead of thetolylene diisocyanate are 3,3'-bitolylene 4,4- diisocyanate, diphenylmethane 4,4-diisocyanate, mphenylenediisocyanate,l,4-cyclohexylenediisocyanate and l,5-naphthylenediisocyanate. Examplesof the polyesters that can be employed are the pol alkylene-etherglycols having molecular wcights of at least 750 and which may be ashigh as about 10,000, e.g. polytetramethylencether glycol,polytrirnethyleneether glycol and polyethylenemethyleneether glycol.Examples of other emulsifying agents that can be used are those marketedunder the trademark name Tween 40 (polyoxyethylene sorbitanmonopalrnitate), Triton N-lOO (Rohm & Haas Co.), and Witco 7786 (WitcoChemical Co).

A second dual bridge structure havingv three steelsupported spans from52 to 73 feet wide crossing a 78- foot road right-of way and, in part, asingle-track railroad was sprayed on its underside with approximately 1inch of polyurethane foam having a density of about 4 pounds per cubicfoot in the same manner as described above. The bridge deck has a 2 /2inch bituminous concrete binder and top course over the concrete base ofapproximately 7 inches.

Although certain preferred embodiments of the invention have beendisclosed for purpose of illustration, it will be evident that variouschanges and modifications may be made therein without departing from thescope and the spirit of the invention.

What is claimed is:

1. An elevated structure carrying Vehicular trafiic having a concretedeck with the upper road surface of said elevated structure and theunderside of said elevated structure exposed to the elements, theimprovement which comprises a layer of about /2 inch to 3 inches thickof cellular plastic material having a density of about 1 to 8 pounds percubic foot bonded to the underside of the concrete surface of theelevated structure carrying vehicular traffic to reduce spalling andretard ice formation on the upper surface of the deck.

2. An elevated structure as claimed in claim 1 wherein the cellularplastic material is urethane foam.

3. An elevated structure as claimed in claim 1 wherein the upper surfaceof the concrete deck is paved with a bituminous layer.

4. An elevated structure carrying vehicular trafiic having a concretedeck with the upper road surface of said elevated structure and theunderside of said elevated structure exposed to the elements, theimprovement which comprises a layer of about inch to 1 /2 inch thick ofcellular plastic material having a density of about 1 /2 to 5 pounds percubic foot bonded to the underside of the concrete surface of theelevated structure carrying vehicular traflic to reduce spalling andretard ice formation on the upper surface of the deck.

5. A method of reducing spalling and improving roadability of theconcrete deck of an elevated structure carrying vehicular traffic andexposed on its upper and lower sides to the elements which comprisesbonding a layer from about inch to 1 /2 inches thick of cellular plasticmaterial having a density of about 1 /2 to 5 pounds per cubic foot tothe underside of the concrete surface of the elevated structure carryingvehicular trafilc.

6. A method of reducing spalling and improving roadability of theconcrete deck of an elevated structure carrying vehicular traffic andexposed on its upper and lower sides to the elements which comprisesapplying urethane foam by spraying to the underside of the concretesurface of the elevated structure carrying vehicular traflic to bond tosaid underside a layer from about /2 to 3 inches thick of urethane foamhaving a density of about 1 to 8 pounds per cubic foot.

7. A method of reducing spalling and improving roadability of abituminous paved concrete deck of an elevated structure carryingvehicular trafiic and exposed on its upper and lower sides to theelements which comprises bonding a layer from about /2 inch to 3 inchesthick of cellular plastic material having a density of about 1 to 8pounds per cubic foot to the underside of the concrete surface of theelevated structure carrying vehicular trafiic.

References Cited in the file of this patent UNITED STATES PATENTS1,728,265 Farnham et a1 Sept. 17, 1929 2,220,349 Plumb Nov. 5, 19402,779,689 Reis Jan. 29, 1957 FOREIGN PATENTS 858,705 Germany Dec. 8,1952 OTHER REFERENCES Plastics, April 1947, pages 18 and 21. ModernPlastics, December 1954, pages 87-92.

1. AN ELEVATED STRUCTURE CARRYING VEHICULAR TRAFFIC HAVING A CONCRETEDECK WITH THE UPPER ROAD SURFACE OF SAID ELEVATED STRUCTURE AND THEUNDERSIDE OF SAID ELEVATED STRUCTURE EXPOSED TO THE ELEMENTS, THEIMPROVEMENT WHICH COMPRISES A LAYER OF ABOUT 1/2 INCH TO 3 INCHES THICKOF